Dopamine-Glutamate Interaction and Antipsychotics Mechanism of Action: Implication for New Pharmacological Strategies in Psychosis

Schizophrenia is a severe mental illness characterized by behavioral and cognitive symptoms. Several lines of evidence focus on a direct involvement of the glutamatergic system in the pathophysiology of psychosis. The hypofunction of the ionotropic glutamate N-methyl-D-Aspartate Receptor (NMDA-R) has been proposed as a model of schizophrenia in humans. Cortical and subcortical glutamate release seems to be modulated by dopaminergic and, to a lesser extent, serotoninergic circuitries, and tuned by intracellular pathways. Although dopamine D2 receptor blockade is a crucial mechanism of antipsychotics pharmacodynamic profile, a putative glutamatergic impact of these compounds is suggested by animal pharmacological isomorphisms of psychosis as well as by clinical studies. According to this view, the balance between D2 antagonism and NMDA-R modulation may be pivotal for the improvement of both positive and negative symptoms. Recently, many pharmacological strategies involving glutamate receptors have been suggested, and novel compounds and pharmacological strategies acting on glutamate transmission are currently under evaluation: i) augmentation strategies improving NMDA-R transmission (glycine, D-serine, Dcycloserine, glycine transporter inhibitors); ii) ampakines, positive modulators of AMPA (a-amino-3-hydroxy-5-methyl- 4-isoxazole propionic acid) receptor complex; iii) agonists of glutamate metabotropic receptors; iv) drugs involved in subcellular adaptation both at pre- and post-synaptic sites. Furthermore, molecular markers, suggesting modulation of glutamate circuitries after antipsychotics administration, are an attractive tool to shed more light on glutamate involvement in antipsychotics mechanism of action. In this review we provide a critical update of recent preclinical and clinical data on dopamine-glutamate interaction and its role in new pharmacological strategies for psychosis treatment